There is an ever-increasing concern about pollution because of the damage it causes to the environment and to human health. One major type of pollution is caused by toxic waste entering and contaminating groundwater supplies. Because of the increased concern regarding groundwater pollution and its possible deleterious affect on the surrounding habitat and on potable water supplies, a large number of groundwater investigations are being conducted. Such groundwater investigations require the collection of water samples at various depths below the ground surface and bringing the samples to the surface for evaluation.
One method used to collect groundwater samples is to sink a permanent well into the ground and pump the water sample to the surface. Constructing permanent wells tends to be more expensive than desired because the equipment is used in only a single location and a separate well must be constructed at each desired sample point.
A second method of groundwater sampling is to take the sample with a device that is not left permanently in the ground, but, instead, is designed to be reused time after time at multiple locations. Such reusable devices incorporate a sample collection chamber (or hollow piping section) which is configured to be driven into the ground to a desired depth so that the water sample can be collected. Once the water sample is in the chamber, the sample is pumped to the surface, or the entire chamber is withdrawn to the surface, so that the sample can be tested.
Commonly, reusable groundwater sampling devices include a drive cone, which is designed to penetrate the earth, permanently mounted on a slotted sample tube configured to telescope within the bottom end of the sample chamber. The drive cone is in abutting relationship with the bottom of the sample chamber with the sample tube housed within the chamber as the device is being driven into the ground. After the device is driven to the desired depth, the sample chamber is withdrawn upwardly a small distance toward the ground surface while, at the same time, the drive cone remains in its original location due to frictional engagement with the ground. Thus, during the withdrawal operation, the sample tube is pulled from its housed position within the sample chamber to expose a portion of its length to the environment. When the sample tube is extended from the sample chamber, a pathway is open for water to flow through the sample tube slots and into the chamber. Some devices are configured so that the sample is pumped from the chamber to the ground surface and, after the sample is taken, the device, including the sample tube and drive cone, is withdrawn from the ground. Other devices are configured to be withdrawn to the ground surface for sample recovery.
In order for the above-described reusable sampling devices to operate properly, the sample tube must be free to slide into and out from the sample chamber during multiple uses and to be restrained within the chamber by a force that is less than the force which restrains the drive cone at its position in the ground. For example, if the sample chamber or the sample tube are bent out of alignment with each other, such that the sample tube is not appropriately free to slide within the chamber, the sample tube will not extend from the chamber, and sampling will not be possible. Thus, when the components are bent out of line, they must be repaired or replaced before the device is used.
Additionally, when groundwater samples are taken in low permeability cohesive soil, it is advantageous to maximize the area from which the water sample can be drawn. By maximizing the sample area, the speed with which the sample chamber fills can be shortened substantially with a resultant reduction in the cost for obtaining the sample. A limitation when using groundwater devices which incorporate sample tubes is that the area from which a sample can be taken is limited to the area along that portion of the length of the tube which extends out from the chamber into the ground. Because it is not practical to provide sample tubes longer than about 5 feet, the sample area can be less than desired when devices incorporating sample tubes are used in low permeability soil.
In view of the foregoing, it is desirable to provide a groundwater sampling device which (1) is of extremely simple construction, (2) minimizes or eliminates components which must maintain the ability to slide within each other in successive uses, and (3) is configured to be capable of maximizing the area from which a sample can be taken, particularly in low permeability cohesive soil.